Surgical Stapling Apparatus With Locking Mechanism

ABSTRACT

The present disclosure provides for a loading unit for use with and/or supportable on a distal end of a surgical stapling apparatus. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism pivotally supported on the housing portion of the loading unit, the locking mechanism having a first position wherein the locking mechanism engages a portion of the drive assembly and maintains the position, preferably the axial position, of the drive assembly relative to the housing portion of the loading unit, and the locking mechanism having a second position wherein the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application claiming thebenefit of and priority to U.S. patent application Ser. No. 11/657,307,filed on Jan. 23, 2007, which is a Continuation Application claiming thebenefit of and priority to U.S. patent application Ser. No. 11/059,773,filed on Feb. 17, 2005, now U.S. Pat. No. 7,225,963, which claims thebenefit of and priority to, U.S. Provisional Patent Application Ser. No.60/545,622, filed on Feb. 17, 2004, the entire contents of eachapplication being incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to a surgical apparatus, e.g., a surgicalstapling apparatus. More particularly, the present disclosure relates toan endoscopic surgical stapling apparatus that includes a lockingmechanism that includes a locking member for retaining the driveassembly of a loading unit, e.g., a single use loading unit (“SULU”) ordisposable loading unit (“DLU”), at a substantially fixed axial positionuntil the SULU or DLU has been loaded with or secured to a surgicalstapling apparatus, to ensure proper or complete engagement of the SULUor DLU, especially its drive assembly, to the surgical staplingapparatus. For simplicity, hereinafter, SULU or DLU will be referred toas “DLU”, but it should be understood to include either or both a DLU orSULU.

2. Background of the Related Art

Surgical devices wherein tissue is first grasped or clamped betweenopposing jaw structure and then joined by surgical fasteners are wellknown in the art. In some instruments a knife is provided to cut thetissue which has been joined by the fasteners. The fasteners aretypically in the form of surgical staples but two part polymericfasteners can also be utilized.

Instruments for this purpose can include two elongated jaw members whichare respectively used to capture or clamp tissue. Typically, one of thejaw members carries a staple cartridge which houses a plurality ofstaples arranged in at least two lateral rows while the other jaw memberhas an anvil that defines a surface for forming the staple legs as thestaples are driven from the staple cartridge. Generally, the staplingoperation is effected by cam members that travel longitudinally throughthe staple cartridge, with the cam members acting upon staple pushers tosequentially eject the staples from the staple cartridge. A knife cantravel between the, staple rows to longitudinally cut and/or open thestapled tissue between the rows of staples. Such instruments aredisclosed, for example, in U.S. Pat. No. 3,079,606 and U.S. Pat. No.3,490,675.

A later stapler disclosed in U.S. Pat. No. 3,499,591 also applies adouble row of staples on each side of the incision. This patentdiscloses a surgical stapler that has a disposable loading unit in whicha cam member moves through an elongate guide path between two sets ofstaggered staple carrying grooves. Staple drive members are locatedwithin the grooves and are positioned in such a manner so as to becontacted by the longitudinally moving cam member to effect ejection ofthe staples from the staple cartridge of the disposable loading unit.Other examples of such staplers are disclosed in U.S. Pat. Nos.4,429,695 and 5,065,929.

Each of the instruments described above is designed for use inconventional surgical procedures wherein surgeons have direct manualaccess to the operative site. However, in endoscopic or laparoscopicprocedures, surgery is performed through a small incision or through anarrow cannula inserted through small entrance wounds in the skin. Inorder to address the specific needs of endoscopic and/or laparoscopicsurgical procedures, endoscopic surgical stapling devices have beendeveloped and are disclosed in, for example, U.S. Pat. No. 5,040,715(Green, et al.); U.S. Pat. No. 5,307,976 (Olson, et al.); U.S. Pat. No.5,312,023 (Green, et al.); U.S. Pat. No. 5,318,221 (Green, et al.); U.S.Pat. No. 5,326,013 (Green, et al.); U.S. Pat. No. 5,332,142 (Robinson,et al.); and U.S. Pat. No. 6,241,139 (Milliman et al.), the entirecontents of each of which are incorporated herein by reference.

Tyco Healthcare Group, LP, the assignee of the present application, hasmanufactured and marketed endoscopic stapling instruments, such as theMultifire ENDO GIA™ 30 and Multifire ENDO GIA™ 60 instruments, for anumber of years. These instruments include a surgical stapling apparatusand a DLU. Typically, the DLU is attached to the apparatus immediatelyprior to surgery. After use, the DLU can be removed from the apparatusand a new DLU can be fastened to the apparatus to perform additionalstapling and/or cutting operations. These instruments have providedsignificant clinical benefits. Nonetheless, improvements to theseinstruments are still possible.

It would be desirable to provide an improved DLU for a surgical staplingapparatus and an improved surgical stapling apparatus having the DLUloaded thereon.

It would also be desirable to provide a locking mechanism for a DLU toassure proper loading of the DLU to the shaft of a surgical staplingapparatus.

Accordingly, it is an object of this disclosure to provide an improvedDLU which locks or retains its drive assembly in proper position to beloaded onto the shaft of a surgical stapling apparatus (hereinafterreferred to as the or a “ready-to-load position”) until the DLU isloaded onto a surgical stapling apparatus to assure that when the DLU isloaded thereto, the drive assembly is properly engaged by, coupled to orconnected to a drive member of the shaft, thereby helping to ensureproper operation of the DLU and the surgical stapling apparatus. Forexample, with the DLU loaded onto the surgical stapling apparatus, afterfiring of the surgical stapling apparatus, retraction of the control rodwill unapproximate or open and/or unclamp the anvil and cartridgeassemblies.

An object of the disclosure is to provide an improved DLU that includesa locking mechanism that retains the drive assembly in such aready-to-load position until the DLU is loaded onto the surgicalstapling apparatus.

Another object of the present disclosure is to provide a lockingmechanism for a DLU and a DLU having a locking mechanism, such thatfiring of the surgical stapling apparatus is prevented unless and untilthe DLU is loaded onto the shaft of the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that, afterfiring, can be disconnected from the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that has onlytwo conditions, one in which it is not loaded and its drive assembly islocked or retained in the ready-to-load position, and another in whichthe DLU is loaded onto the shaft of a surgical stapling apparatus and inwhich the drive assembly is unlocked and free to be actuated.

Still another object of the present disclosure is to provide the aboveobjects in a roticulating, i.e., roticulable, DLU.

SUMMARY

In accordance with the present disclosure, a surgical apparatus, e.g., asurgical stapling apparatus, including a locking mechanism for ensuringproper engagement of a disposable loading unit to an end, preferably thedistal end, of the surgical apparatus is provided. According to oneaspect of the present disclosure, the surgical apparatus includes ahousing, a handle supported by the housing, and a loading unitsupportable on a distal end of the housing. The loading unit includes ahousing portion including a distal end and a proximal end, a driveassembly slidably supported within the housing portion of the loadingunit, and a locking mechanism pivotally supported on the housing portionof the loading unit. The locking mechanism can have a first positionwherein the locking mechanism engages a portion of the drive assemblyand maintains the position of the drive assembly relative to the housingportion of the loading unit. The locking mechanism can have a secondposition wherein the locking mechanism disengages the drive assembly andenables the drive assembly to move relative to the housing portion.

It is envisioned that the locking mechanism can include a leverpivotably connected to the housing portion ad defining a pivot point.The lever includes a distal end extending distally of the pivot pointand a proximal end extending proximally of the pivot point. The distalend of the lever preferably includes a member, preferably a hook, forselectively engaging the portion of the drive assembly, wherein when thelocking mechanism is in the first position the hook engages a portion ofthe drive assembly and when the locking mechanism is in the secondposition the hook is disengaged from the portion of the drive assembly.

It is envisioned that when the locking mechanism is moved from the firstposition, to the second position the proximal end of the lever is movedradially inward and the distal end of the lever is moved radiallyoutward. The locking mechanism is moved from the first position to thesecond position upon the coupling of the loading unit to the distal endof the elongate body. Preferably, the locking mechanism is moved fromthe first position to the second position by a twisting action of theloading unit relative to the elongate body when the insertion tip of theloading unit is inserted in to the distal end of the elongate body.

The locking mechanism can further include a biasing member operativelyassociated therewith. Preferably, the biasing member biases the lever tothe first-position.

It is envisioned that when the locking mechanism is in the firstposition, the proximal-end of the lever extends radially beyond an outersurface of the housing portion. Desirably, the proximal end of the leverof the locking mechanism may define an angled surface to facilitateconnection with the elongate body.

Preferably, the surgical apparatus is a fastener applier or stapler,preferably a laparoscopic or endoscopic stapler.

This disclosure also is of a DLU, preferably a roticulator DLU for asurgical fastener applier or stapler.

Desirably, the proximal end of the housing portion of the loading unitdefines an insertion tip.

It is envisioned that the surgical apparatus may include an elongatebody extending distally from the housing.

The present disclosure further provides for a loading unit for use withand/or supportable on a distal end of a surgical stapling apparatus. Theloading unit includes a housing portion including a distal end and aproximal end, a drive assembly slidably supported within the housingportion of the loading unit, and a locking mechanism supported on thehousing portion of the loading unit, the locking mechanism having afirst position wherein the locking mechanism engages a portion of thedrive assembly and maintains the position, preferably the axialposition, of the drive assembly relative to the housing portion of theloading unit, and the locking mechanism having a second position whereinthe locking mechanism disengages the drive assembly and enables thedrive assembly to move relative to the housing portion.

Additional advantages will become apparent from the description whichfollows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be further described with reference to theaccompanying drawings, wherein like reference numerals refer to likeparts in the several views, and wherein:

FIG. 1 is a top perspective view of a preferred embodiment of thepresently disclosed surgical stapling apparatus;

FIG. 2 is a top view of the surgical stapling apparatus shown in FIG. 1;

FIG. 3 is a side view of the surgical stapling apparatus shown in FIGS.1 and 2;

FIG. 4 is a top perspective view of the surgical stapling apparatus ofFIGS. 1-3 with the DLU disengaged from the elongate body of the surgicalstapling apparatus;

FIG. 5 is a bottom perspective view of a non-articulating DLU for usewith the surgical stapling apparatus of FIGS. 1-4;

FIG. 6 is a bottom perspective view of the preferred articulating DLU ofthe surgical stapling apparatus of FIGS. 1-4;

FIG. 7 is a top perspective view of the DLU of FIG. 6;

FIG. 8 is a top perspective view of the DLU of FIGS. 6 and 7;

FIG. 9 is an enlarged top perspective view, with parts separated, of theproximal housing portion and mounting assembly of the DLU of FIGS. 6-8;

FIG. 9 a is an enlarged top perspective view of the proximal portion ofthe upper housing half of the DLU of FIGS. 6-9;

FIG. 10 is a top perspective view of the proximal housing portion andmounting assembly of the DLU of FIGS. 6-9 with the upper housing halfremoved;

FIG. 11 is a top perspective view, with parts separated, of the axialdrive assembly of the DLU of FIGS. 6-9;

FIG. 12 is a top perspective view of the axial drive assembly of FIG. 11of the DLU of FIGS. 6-9;

FIG. 13 is an enlarged top perspective view of a lower housing half ofthe proximal housing portion of the DLU of FIGS. 6-9;

FIG. 14 is an enlarged perspective view of the distal end of theelongated body of the stapling apparatus shown in FIG. 4;

FIG. 15 is an enlarged perspective view of the proximal end of the DLUof FIGS. 6-9 illustrating a locking mechanism according to the presentdisclosure;

FIG. 16 is an enlarged perspective view of a distal end of the elongatebody of the stapling apparatus in accordance with the presentdisclosure;

FIG. 17 is an enlarged perspective view, partially broken-away, of theproximal end of the DLU of FIG. 15 illustrating the locking mechanism ina first position;

FIG. 18 is a longitudinal cross-sectional view of the proximal end ofthe DLU of FIGS. 6-9, as taken through 18-18 of FIG. 15, with thelocking mechanism in a first position;

FIG. 19 is an enlarged perspective view, partially broken-away, of theproximal end of the DLU of FIG. 15 illustrating the locking mechanism ina second position;

FIG. 20 is a longitudinal cross-sectional view of the proximal end ofthe DLU of FIGS. 6-9 as taken through 18-18 of FIG. 15, with the lockingmechanism in a second position;

FIG. 21 is an enlarged transverse cross-sectional view of the proximalend of the DLU of FIGS. 6-9, as taken through 21-21 of FIG. 18;

FIG. 22 is an enlarged transverse cross-sectional view of the proximalend of the DLU of FIGS. 6-9, as taken through 22-22 of FIG. 20,illustrating the position of the locking mechanism prior to the rotationof the DLU relative to the elongate body; and

FIG. 23 is an enlarged transverse cross-sectional view of the proximalend of the DLU of FIGS. 6-9, as would be taken through 22-22 of FIG. 20,illustrating the position of the locking mechanism following rotation ofthe DLU relative to the elongate body.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the presently disclosed surgical apparatus, DLUand locking mechanism or member will now be described in detail withreference to the drawings, in which like reference numerals designateidentical or corresponding elements in each of the several views.

In the drawings and in the description that follows, the term“proximal”, as is traditional, will refer to the end of the staplingapparatus which is closest to the operator, while the term “distal” willrefer to the end of the apparatus which is furthest from the operator.

FIGS. 1-4 show a surgical apparatus, e.g., surgical stapling apparatus,generally referred to as 10. In the interest of brevity, this disclosurewill focus primarily on systems, methods and structures for loading,engaging, coupling or connecting a disposable loading unit (“DLU”) 16 tosurgical stapling apparatus 10. A detailed discussion of the remainingcomponents and method of use of surgical stapling apparatus 10, isdisclosed in U.S. Pat. No. 6,241,139.

Surgical stapling apparatus 10 is an endoscopic apparatus and includes ahandle assembly 12 and an elongated body 14 extending from handleassembly 12. A DLU 16 is releasably secured to the distal end ofelongated body 14. While this disclosure relates to the use of a DLUwith surgical stapling apparatus 10, it is understood and within thescope of the present disclosure that a single use loading unit (SULU) orother end effector and/or tool assembly can equally be used incooperation with surgical stapling apparatus 10.

DLU 16 includes a tool 17 having a cartridge assembly 18 housing aplurality of surgical staples (not shown) and an anvil assembly 20movably secured in relation to cartridge assembly 18. As shown herein,DLU 16 is configured to apply six (6) linear rows of staples, in DLU'smeasuring from about 30 mm to about 60 mm in length, DLUs for applyingany number of rows of staples, having staple pockets arranged in variouspatterns and/or DLUs and end effectors having any other lengths, e.g.,45 mm, are also envisioned. Handle assembly 12 includes a stationaryhandle member 22, a movable handle member 24, and a barrel portion 26.

A rotatable member 28 preferably is mounted on the forward end of barrelportion 26 to facilitate rotation of elongated body 14 and attached DLU16 with respect to handle assembly 12. An articulation lever 30preferably is also mounted on the forward end of barrel portion 26adjacent rotatable member 28 to facilitate articulation of tool assembly17. Preferably, a pair of knobs 32 are movably positioned along barrelportion 26. Knobs 32 are advanced distally to approximate or closecartridge and/or anvil assembly 18, 20, and retracted proximally tounapproximate or open cartridge and/or anvil assembly 18, 20.

As seen in FIG. 4, DLU 16 is desirably selectively removably couplableto elongated body 14. DLU 16 includes a housing portion 200 having aproximal end adapted to releasably engage the distal end of elongatedbody 14. A mounting assembly 202 is pivotally secured at 203 to thedistal end of housing portion 200, and is configured to receive theproximal end of tool assembly 17 such that pivotal movement of mountingassembly 202 about an axis at 203 perpendicular to the longitudinal axisof housing portion 200 effects articulation of tool assembly 17.

Surgical stapling apparatus 10 is capable of receiving anon-articulating DLU 16 a, as seen in FIG. 5, or an articulating DLU 16,as seen in FIGS. 6-8. U.S. Pat. No. 6,241,139 includes a detaileddiscussion of articulating and non-articulating DLU.

With general reference to FIGS. 9, 9 a, 10-13, 15 and 17-23 andparticular reference to FIGS. 9, 9 a, 15, 17 and 18, DLU 16 includes amounting assembly 235. Mounting assembly 235 includes an upper and alower mounting portion 236, 238, respectively. A centrally located pivotmember 284 extends from each of upper and lower mounting portions 236,238 through respective openings 246 a formed in coupling members 246.Coupling members 246 each include an interlocking proximal portion 246 bconfigured to be received in grooves 290 formed in the proximal end ofupper and lower housing halves 250, 252 to retain mounting assembly 235and upper and lower housing halves 250, 252 in a longitudinally fixedposition in relation to each other.

Upper housing half 250 and lower housing half 252 are contained withinan outer sleeve, shell or casing 251. The proximal end of upper housinghalf 250 includes radially outwardly extending engagement nubs 254 forreleasably engaging the distal end of body 14. Nubs 254 form abayonet-type coupling with the distal end of body 14. Housing halves 250and 252 define a channel 400 for slidably receiving axial drive assembly212 therein. An articulation link 256 is dimensioned to be slidablypositioned within a slot 402 formed in upper and lower housing halves250, 252. A pair of blow out plate assemblies 255 are positionedadjacent the distal end of housing portion 200 adjacent the distal endof axial drive assembly 212 to prevent outward buckling and bulging ofdrive assembly 212 during articulation and firing of surgical staplingapparatus 10. For a detailed discussion of the structure and operationof blow out plate assemblies 255, reference is made to InternationalApplication Serial No. PCT/JUS02/32031, filed on Oct. 4, 2002, entitled“Surgical Stapling Device”, the entire content of which is hereinincorporated by reference.

Referring to FIG. 9, optionally, a locking member 288 may be supportedon engagement section 270 of axial drive assembly 212. In operation,when axial drive assembly 212 is actuated, by applying a predeterminedforce to movable handle member 24 to advance axial drive assembly 212distally, locking member 288 provides an audible and tactile indicationthat surgical stapling apparatus 10 has been actuated. For a detaileddiscussion of the structure and operation of locking member 288,reference is made to the aforementioned International Application SerialNo. PCT/US02/32031. Locking member 288 may also prevent inadvertentpartial actuation of DLU 16, such as during shipping, by locking axialdrive assembly 212 at a fixed position within DLU 16 until apredetermined axial force has been applied to axial drive assembly 212.

With reference to FIGS. 9-12, axial drive assembly 212 includes anelongated drive beam 266 (FIG. 11) including a distal working head 268(FIG. 12) and a proximal engagement section 270. Drive beam 266 may beconstructed from a single sheet of material or, preferably, multiplestacked sheets, as shown in FIG. 11. Engagement section 270 includes apair of resilient engagement fingers 270 a and 270 b which aredimensioned and configured to mountingly engage a pair of correspondingretention slots 272 a and 272 b formed in drive member 272 (FIG. 12).Drive member 272 includes a proximal porthole 274 configured to receivedistal end 276 of a drive member, e.g., drive rod or control rod 52(FIGS. 14 and 16-18) when the proximal end of DLU 16 is being engagedwith elongated body 14 of surgical stapling apparatus 10. Control rod 52functions to impart axial movement of drive assembly 212 from handleassembly 12.

With reference to FIGS. 9, 9 a and 15-32, DLU 16 further includes alocking mechanism 300, preferably pivotably supported on a housing,e.g., on upper housing half 250. Locking mechanism 300 is manipulatablefrom a first position, in which drive assembly 212 is maintained in aready-to-load position for proper loading, to a second position, inwhich drive assembly 212 is free to move. DLU 16 is considered to beloaded-to elongate body 14 when locking mechanism 300 is in the secondposition, i.e., when drive assembly 212 is connected to control rod 52of elongate body 14. As seen in FIGS. 9, 9 a and 15-23, lockingmechanism 300 includes a lever 302 pivotally connected to upper housinghalf 250 by a pivot pin 308 extending therethrough, thereby defining apivot point. Lever 302 includes a free distal end 304 extending distallyof pivot pin 308 and a free proximal end 306 extending proximally ofpivot pin 308. Proximal end 306 of lever 302 terminates in an angledsurface 306 a formed along an upper surface thereof for engaging aportion of elongate body 14, as will be discussed in greater detailbelow. Distal end 304 of lever 302 terminates in a hook member 304 aformed along a lower surface thereof for engaging drive member 272, aswill be discussed in greater detail below.

Locking mechanism 300 further includes a biasing member or spring 312,preferably a leaf spring, operatively associated with upper housing half250 and distal end 304 of lever 302. Preferably, spring 312 maintainslever 302 in the first position such that hook member 304 a is engagedwith drive member 272. Spring 312 includes a proximal end 312 aoperatively associated with distal end 304 of lever 302, and a distalend 312 b secured to upper housing half 250. Preferably, distal end 312b is in the form of a hook or bent arm extending into a slot or groove250 a (see FIGS. 17-20) in upper housing half 250 in such a manner so asto create a force “F” acting radially inward at proximal end 312 a ofspring 312 (see FIG. 17). Proximal end 312 a is positioned in engagementwith an outer surface 304 b of distal end 304 of lever 302. As such,force “F” in turn acts on distal end 304 of lever 302 to thereby urgedistal end 304 radially inward as well. In so doing, proximal end 306 oflever 302 is urged radially outward due to the pivoting action of lever302 about pivot pin 308.

Prior to attachment of DLU 16 to surgical stapling apparatus 10, lever302 of locking mechanism 300 is urged to the locked position by spring312 (FIGS. 15, 17 and 18). As discussed above, in the locked position,lever 302 is pivoted about pivot pin 308 such that hook member 304 a oflever 302 is in engagement with a distal face 272 c, of drive member 272and proximal end 306 is positioned radially outward of an outer surface193 a of insertion tip 193 (see FIG. 18). In this locked position, hookmember 304 a prevents inadvertent distal advancement of drive member 272to maintain drive member 272 in its proximal-most ready-to-loadposition. This ensures that engagement section 270 of drive assembly 212properly engages the distal end 276 of control rod 52 (see FIG. 14) ofstapling apparatus 10 when DLU 16 is mounted to elongated body 14 ofstapling apparatus 10. Distal end 276 of control rod 52 has one or moreengagement surfaces, preferably, and here shown as, including a head 276a and a smaller diameter annular recess 276 b just proximal of head 276a and partially defined by head 276 a.

When DLU 16 is mounted to elongated body 14 of stapling apparatus 10, ina manner to be discussed in further detail below, angled surface 306 aof proximal end 306 of lever 302 engages sloping surface 276 f ofelongate body 14 (see FIGS. 20, 22 and 23). Engagement between angledsurface 306 a and sloping surface 276 f pivots or rotates lever 302about pivot pin 308 to cam proximal end 306 of lever 302 radiallyinwardly. Movement of proximal end 306 radially inwardly effectsmovement of hook 304 a radially outwardly against force “F” of spring312, such that hook 304 a is released from and/or otherwise disengagedfrom drive member 272 to free drive assembly 212 and enable theoperation or continued operation of surgical stapling apparatus 10.

As best seen in FIG. 16, preferably the distal end of elongate body 14includes a recess 276 e formed therein having a shape to facilitatemanipulation of locking mechanism 300 from the first position to thesecond position. Preferably, recess 276 e includes a sloping surface 276f against which angled surface 306 a of lever 302 contacts. Inparticular, sloping surface 276 f is shaped such that twisting of DLU 16in relation to elongated body 14 of stapling apparatus 10, afterinsertion tip 193 of DLU 16 has been inserted into the distal end ofelongate body 14, results in proximal end 306 of lever 302 beingprogressively urged or cammed radially inward. Only after DLU 16 hasbeen rotated over a sufficient arc in relation to body 14 will proximalend 306 of lever 302 be cammed radially inwardly a distance sufficientto release hook member 304 a from drive member 272.

With continued reference to FIGS. 15-23, a method of use and/oroperation of locking mechanism 300, when securing DLU 16 to the distalend of elongate body 14, will be discussed. Initially, with lockingmechanism 300 in the first position such that hook 304 a is inengagement with drive member 272, insertion tip 193 of DLU 16 isintroduced longitudinally into the distal end of elongate body 14, ineither direction of arrow “A” (FIG. 19). As seen in FIGS. 19, 20 and 22,during introduction of insertion tip 193 into the distal end of elongatebody 14, proximal end 306 of lever 302 enters recess 276 b (FIG. 20)formed in the distal end of elongate body 14.

When insertion tip 193 has been fully inserted into the distal end ofelongate body 14, and more particularly, when nubs 254 have completelyentered channels 276 d (FIGS. 16, 22 and 23), DLU 16 is rotated, in thedirection of arrow “B” (FIGS. 19 and 23), such that sloping surface 276f of recess 276 e acts against and engages angled surface 306 a ofproximal end 306 of lever 302. As described above, the eamming actionbetween sloping surface 276 f of recess 276 e and angled surface 306 aof proximal end 306 causes proximal end 306 of lever 302 to be urgedradially inward, as indicated by arrow “C” of FIG. 23, and about pivotpin 308, thereby overcoming force “F” of spring 312, and urging distalend 304 radially outward such that lever 302 is urged from the firstposition to the second position. Displacement of distal end 304 in aradially outward direction results in hook 304 a becoming disengagedfrom drive member 272 thereby freeing drive assembly 212 for thecontinued operation of surgical stapling apparatus 10. DLU 16 isconsidered to be loaded to elongate body 14 when lever 302 is in thesecond position, e.g., when drive assembly 212 is connected to drivemember or control rod 52 of elongate body 14.

Accordingly, the attachment of a DLU, having a drive assembly 212, tothe distal end of elongate body 14 when drive assembly 212 is not in itsproximal-most or proper loading position is prevented.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplifications ofpreferred embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1-20. (canceled)
 21. A method of securing a disposable loading unit to asurgical fastener applying apparatus, the method comprising the stepsof: inserting a proximal end of the disposable loading unit into adistal end of an elongate body portion of the surgical fastener applyingapparatus; and rotating the disposable loading unit relative to theelongate body portion of the surgical fastener applying apparatus tomove a locking mechanism associated with the disposable loading unitfrom a first position, wherein a drive assembly of the disposableloading unit is maintained in a substantially fixed position to preventfiring of the surgical fastener applying apparatus, to a secondposition, wherein the drive assembly of the disposable loading unit isfree to move to permit firing of the surgical fastener applyingapparatus, and moving proximal and distal ends of the locking mechanismin opposing radial directions relative to a longitudinal axis of thedisposable loading unit.
 22. The method of claim 21, further comprisingthe step of moving the distal end of the locking mechanism out ofengagement with the drive assembly of the disposable loading unit. 23.The method of claim 22, wherein the step of moving the distal end of thelocking mechanism includes the steps of: moving the proximal end of thelocking mechanism radially inward towards the longitudinal axis of thedisposable loading unit; and moving the distal end of the lockingmechanism radially outward away from the longitudinal axis of thedisposable loading unit.
 24. The method of claim 23, wherein the step ofinserting the proximal end of the disposable loading unit into thedistal end of the elongate body portion includes the step of insertingthe proximal end of the locking mechanism into a recess formed in thedistal end of the elongate body portion.
 25. The method of claim 24,wherein the step of inserting the proximal end of the locking mechanisminto the recess includes the step of engaging corresponding angledsurfaces defined by the recess and the proximal end of the lockingmechanism.
 26. The method of claim 21, wherein the step of moving theproximal and distal ends of the locking mechanism includes the step ofpivoting the locking mechanism about a pivot point.
 27. The method ofclaim 21, further comprising the step of displacing a biasing member inengagement with the locking mechanism, wherein the biasing member urgesthe locking mechanism towards the first position.
 28. The method ofclaim 21, wherein the step of inserting the proximal end of thedisposable loading unit into the distal end of the elongate body portionincludes the step of positioning projections formed on the disposableloading unit within corresponding channels formed in the elongate bodyportion.
 29. A method of assembling a surgical fastener applyingapparatus including a handle assembly, an elongate body portionextending distally from the handle assembly, and a disposable loadingunit that includes a tool assembly configured and dimensioned to retainand form a plurality of surgical fasteners, the method comprising thesteps of: inserting a proximal end of the disposable loading unit into adistal end of the elongate body portion; and rotating the disposableloading unit relative to the elongate body portion to cause engagementbetween a first camming surface formed at the distal end of the elongatebody portion, and a second camming surface formed on a locking mechanismassociated with the disposable loading unit to move the lockingmechanism from a first position, wherein a drive assembly of thedisposable loading unit is maintained in a substantially fixed positionto prevent firing of the surgical fastener applying apparatus, to asecond position, wherein the drive assembly of the disposable loadingunit is free to move to permit firing of the surgical fastener applyingapparatus.
 30. The method of claim 29, further comprising the step ofpivoting the locking mechanism about a pivot point.
 31. The method ofclaim 30, wherein the step of pivoting the locking mechanism includesmoving proximal and distal ends of the locking mechanism in opposingradial directions relative to a longitudinal axis of the disposableloading unit.
 32. The method of claim 31, wherein the step of pivotingthe locking mechanism includes the step of moving the distal end of thelocking mechanism out of engagement with the drive assembly of thedisposable loading unit.
 33. The method of claim 32, wherein the step ofpivoting the locking mechanism includes the steps of: moving theproximal end of the locking mechanism radially inward towards thelongitudinal axis of the disposable loading unit; and moving the distalend of the locking mechanism radially outward away from the longitudinalaxis of the disposable loading unit.